气井油套合采时井底流压的计算方法

气井井底流是分析气井生态动态的重要参数之一，目前国内外很少报道油套合采时井底流压的计算方法。运用流体力学原理，将气井油套合采简化假设成并联管路流动，基于油管生产和油套环空生产时井底流压的计算公式，推导了油套合采时油管和油套环空的产量分配公式，通过分析公式中各项的权重，得出油管和油套管环空产量分配的简化式，从而将油套合采时井底流压计算转化成油管生产或油套环控生产时井底流压的计算，计算表明，采用简化产量分配公式与精确产量分配公式所计算的井底流压，相对误差很小，说明建立的油套合采时井底流压的计算方法可靠，具有较强的实用性。

Method of Wellbore Pressure Calculation for Tubing-Casing Productiom System of Gas Wells

Wellbore pressure is an important parameter in gas well performance analysis. However, reports on the method of wellbore pressure calculation for tubing-casing production system (TCPS) of gas wells are rare. Applying the hydrodynamics fundamentals, the TCPS is treated as a parallel connection of tubing and casing production. Based on the wellbore pressure calculation method for the cases of tubing production system and the system of production from the annul space between the casing and the tubing, we obtained an equation describing the allocated production from the casing and the tubing. By analyzing the weighted importance of each item in the equation, a simplified production distribution equation is obtained, which translate the wellbore pressure calculation for the TCPS into one for tubing and (or) casing production system. An example is given which shows that the relative error between the result obtained by using the proposed equation and that by using the accurate production distribution equation is very small, indicating that proposed method is reliable and applicable.